Method of forming tubes



i G. G. HARRINGTON METHOD OF FORMING TUBES Filed Aug. 13 1941 George 6: Hdrr/Zyfan.

INVENTOR. M

Patented Dec. 2; W43

assets? TBS WTHOD F FORWG TUBES George G. Harrington, Houston, Tern, assignor to Reed Roller Bit Company, Houston. 'ilem, a

corporation or Texas Application August 16, 1941, Serial No; dil'idldd (Cl. til-$2) Ii. Claim.

This invention relates to the manufacture of tubes or pipes and has for its general object the provision of a method of manufacturing an improved pipe having relatively thin walls throughout the major portion of its length but having relatively thick walled end sections.

Pipe of the character'referred to is useful in numerous situations and particularly is it used for making up the drill stem used in drilling deep wells by the rotary drilling method.

Heretofore such pipe has been manufactured from pie-formed tubes which are relatively thin walled throughout their length, having been originally manufactured with a wall thickness substantially the same as the wall thickness desired for the major portion of th length of the tube.

The end sections of the tube are then made with thicker walls either by up-setting the metal of the tube or by welding or otherwise securing additional metal on the exterior surface of the tube. The welding or securing or other metalon the exterior surface of the tube does not add to the tube the strength and other characteristics desired and is not generally employed. The method usually employed is that of up setting the metal of the tube adjacent its ends to form thick walled end sections of the tube. However, the process of so up-setting the metal of the tube to form thick walled end sections has been found to Produce an undesirable distortion of the granular arrangement of the tube metal and to result in a decreased strength and resistance to fatigue at the location of the up-set. Many and various means have beensought ior providing the thickened end sections on such tubes without this dis= tortion of the arrangement of the grain structure and the consequent irregular flow lines in the grain structure at the upset.

It is an object of this invention to produce a tubular member having thickened end sections, such as above referred to, without the distorted flow lines in the, granular structure, and to -provide a method (if making such tubular member.

Another object of this invention is toproduce such a tubular member in which the flow lines from the relatively thin to the relatively thick walled sections will be smooth and undistorted and to provide a method for making the same.

The objects of this invention have been obtained in an entirely difierent manner from that in which tubular members with up-set ends have been provided in the past. In substance the tubular member is never formed with a complete thin walled cross section from end to end. In-

stead, the tubular member is in accordance with this invention formed from a tubular member having a wall thickness from end to end'substantially the same as the wall thickness desired for the end sections of the finished tool. The intermediate portion of such thick walled tubular member is then rolled by placing a mandrel within the tubular member and rolling its Outer surface to reduce its wall thickness and increase its a length intermediate its ends only. The end portions which form the end sections of the finished tube are not reduced or rolled during this process.

It is appreciated that thin walled tubular members have been formed in the past by placing a. mandrel within a tubular billet and then rolling the exterior of said billet from end-to end to produce the desired wall thickness of the tubular member. Such rolling, however, has ordinarily been commenced at one end of such billet and has proceeded to the other end thereof. No attempt has been made to roll an intermediate portion or such tilllet only for the purpose of producing a tubular member with thick walled and sections that would. have smooth flowlines therein. It has now been discovered that a tubular member having thick walled end sections mav be produced in the manner above set forth by rolling the intermediate portions only and that a tubular member thus produced will have smooth flow lines in. its granular structureand will not have either an abrupt change in the arrangement of the granular structure nor any substantial distortion or such granular structure as occurs in the case of the previously employed rip-setting method of being broken away and shown in longitudinal cross section;

Fig. 2 is a side elevation member sho intermedia producing tn nished tubular member in the form desired;

of the same tubular the operation of rolling the Fig. 3 is a view on an enlarged scale partly in I side elevation and partly in longitudinal cross section showing a completed tubular member constructed in accordance with this invention.

. The member i shown in Fig. 1 represents the tubular member which is employed by this invention in the production of the desired finished tion thereof for the purpose oi tube. This tubular member has walls 2 of substantially the thickness which is desired that the end sections of the finished tube shall have and it has an opening 3 therethrough which is substantially the same "diameter as the opening which will extend through the finished tube. Through this opening 3 at the beginning of the process of this invention there is placed a mandrel 4 of substantially the same diameter as the opening 3. Rollers I and 8 are then brought into contact with the outside surface of the member I intermediate its ends. These rollers I and 6 are v larger at their ends than at their central portions and 'are preferably in the form of hyper- I boloids of revolution. 1 They are carried by a suitable rolling mill device of any well known form.

. By the use of the rollers and I, the intermediate portion of the body I is rolled toward the opposite ends thereof to form the main portion] of the tubular member, which is relatively thin walled. .The end portions of the body I are not rolled but are allowed to remain their'original thickness as indicated at 0 and 9.

After the rolling operation has been completed the ends of the tubular member in the thick walled portionsmay be threaded internally and externally as at Ill and II if so desired or may be otherwise prepared for connection to other members.

Referring particularly to Fig. 3, it is to be noted that the flow lines I2 formed by the crystalline arrangement of the material in the portion I are Joined smoothly as shown at II with the flow lines I4 in'the thicker end sections 8. There is no abrupt change in the crystalline arrangement and the smooth flow lines blending from the thick to the thin sections and vice versa provide a relatively strong member at its iuncture and one which will not be any more susceptibleto fatigue than the remainder of the tube.

the desired characteristics hereinbefore stated and which is capable of accomplishing all of the objects of this invention. Having described my invention, I claim: The method of forming relatively thin walled tubes with relatively thick walled end sections which comprises rolling the intermediate portion of a relatively short thick walled tubular memher having inner and outer diameters from end to end substantially the same as desired for the end sections of the finished tube, said rolling operation including placing said member over a mandrel of substantially the same size as the opening through said member, and subjecting the intermediate portion of said tube to the action of a pair of opposed skewed rollers to reduce the wall thickness of said intermediate portion to the thickness desired for the finished tube, and causing said rollers to form a tapered section betweenthe relatively thick end sections left by said rolling operation and the relatively thin walled intermediate section, whereby the flow lines of the crystalline formation of the ma--.

terial of said tube will be relatively smooth and continuous between said relatively thick and relatively thin walled portions.

GEORGE G. HARRINGTON.

A method has thus been provided which is capable of producing a tubular member having 

